The present invention relates to a stacking device for packaging machines to form groups of products arranged side to side and to insert the groups into cartons. The invention applies in particular to packaging machines for making tea bags or similar infusable products but, although the present description specifically refers to these products, it may also be conveniently applied to the stacking and cartoning of products of various other kinds, or their packages, having similar properties of flexibility and pliability.
In the automatic tea-bag making sector, numerous machines are known (as described, for example, in Italian patent application No. BO95A000574 made by the same Applicant as the present). These machines make a continuous tube of filter paper containing charges of infusable product and transversely sealed at regular intervals, each portion of tube thus formed containing a single charge of product. As it feeds continuously along the machine, the tube passes through a cutting station, which makes a continuous succession of tea bags by cutting the tube at regular intervals. The tea bags made in this way are stacked in groups or batches containing a predetermined number of tea bags which are then inserted into cartons.
The main problem of packaging the tea bags is to synchronize the continuous motion of the machine which makes the tea bags with the alternating motion of the one which stacks and cartons the individual groups of tea bags.
One known solution to this problem which reflects customary packaging techniques is to provide devices consisting in particular of a vertical stacking line located downstream of the cutting station and a cartoning station located beside the stacking line. The stacking line is equipped with a controlled outfeed hopper into which the continuous stream of products from the cutting station is fed. Inside the hopper, there is an alternating presser which pushes the products one by one into a container located below. Inside the container, a movable tongue actuated in such a manner as to retain the single products and push them down the container to form a stack which extends downwards towards the endwall of the container itself.
When the predetermined number of products is reached, the hopper is closed and the container moves from an initial condition in which it is connected with the hopper to a final position in which it is connected with the cartoning station. At the latter, the stack is extracted from the container and inserted into a carton, after which the container returns to the initial condition, the hopper re-opens and the sequence is repeated for the next batch of products.
To enable this sequence to be suitably synchronized with the products feeding out of the tea bag maker, known devices envisage complex mechanical systems. These consist essentially of a shaft that rotates at a speed connected with the speed of the tea bag maker, so as to enable the products forming part of the group to be counted, and separating devices which, on reaching the predetermined number of products in a batch, separate the batch on a command issued by cam-operated elements.
Although the devices of this kind operate satisfactorily, the considerable complexity of their construction involves high costs.
Another disadvantage is that it is impossible to rapidly effect size changeover by changing the number of products in a group. In fact, even if their drive systems are equipped with mechanical adjustment means which, moreover, further increase the constructional complexity of the devices as a whole, the changeover procedure requires lengthy adjustments which are economically justified only if very large numbers of batches with the same number of tea bags are to be made.
The present invention has for an object to provide a device designed to form groups of products and insert them into cartons which is simple and economical in construction and which thus overcomes the disadvantages mentioned above.